This invention relates to a vibratory mechanism for a compacting machine and more specifically to a vibratory mechanism that is selectable between a variety of distinct amplitude and frequency settings.
Compacting work machines are supported on one or more rotating drums that are used to roll over compactable materials, such as soil and aggregates, during the fabrication of roadways. The rotating drums include vibratory mechanisms mounted coaxially within the rolling drum to increase the compacting force during operation. It is desirable to have a mechanism that is adjustable so as to vary the amplitude and frequency of the compacting force so that the compacting machine is always at peak efficiency.
Many different vibratory mechanisms have been developed and used that create variable amplitude and frequency vibratory forces for compacting. However, many of these mechanisms are complicated and use a number of moving parts to index one eccentric weight relative to another to obtain a variable amplitude force. One such mechanism is disclosed in U.S. Pat. No. 4,481,835 issues on Nov. 13, 1985 and assigned to Dynapac Maskin AB. This system utilizes a first/outer cylindrical eccentric weight coaxially aligned with a second/inner cylindrical eccentric weight, both weights are rotatably supported on a shaft. The weights are drivingly connected to the shaft by a pin that is diametrically positioned through spiral grooves in the outer weight and a pair of spiral grooves in the inner weight and the shaft. The grooves in the outer weight spiral in the opposite direction of the outer weight. The rod of a single action hydraulic cylinder is positioned in an axial hollow opening of the shaft so as to push against the pin. When the rod is extended the outer weight and the inner weight index relative to one another via the spiral grooves. A spring is used to return the weights to a fixed position. This system is effective but complicated and requires a hydraulic cylinder to be rotatably mounted coaxial with a fluid drive motor that propels a rolling drum.
The present invention is directed to overcome one or more of the problems as set forth above.
In one aspect of the present invention a vibratory mechanism is provided. The vibratory mechanism includes a first eccentric weight having a first and a second stub shaft, which are rotatably supported by a pair of bearings. A second eccentric weight is coaxially rotatably supported on a shaft positioned within the first eccentric weight. A movable mass is contained within a hollow cavity in the second eccentric weight. An adjustment shaft is coaxially positioned within the first stub shaft and is operatively connected to the first and second eccentric weights and used for indexing the second eccentric weight relative to the first eccentric weight. Lastly, a motor is attached with the second stub shaft.